How To Debug js code in the board?

Ok, I've just come up with a branch for the debugger.

There should be builds with it in here

To use it, try uploading:

function hang_me() {
  while (true) {
    digitalWrite(LED1,1);
    digitalWrite(LED1,0);
  }
}

function bob() {
  console.log(1);
  hang_me();
  console.log(2);
}

• Then type bob() on the left. It'll hang because of the while(true).
  
• Press Ctrl-C - it'll show where you are in the code, with debug> prompt
  

• Then you can type in commands to do stuff

  >bob()
  1
  while (true) {
              ^
  debug>
  In debug mode: Expected a simple ID, type 'help' for more info.
  debug>help
  Commands:
  help / h           - this information
  quit / q / Ctrl-C  - Quit debug mode, break execution
  continue / c       - Continue execution
  next / n           - execute to next line
  step / s           - execute to next line, or step into function call
  print ... / p ...  - evaluate and print the next argument
  debug>n
  digitalWrite(LED1,1);
  ^
  debug>n
  digitalWrite(LED1,0);
  ^
  debug>n
  }
  ^
  debug>n
  }
  ^
  debug>n
  digitalWrite(LED1,1);
  ^
  debug>q
  Execution Interrupted
  at line 2 col 14
  while (true) {
           ^
  in function "hang_me" called from line 3 col 11
  hang_me();
        ^
  in function "bob" called from line 1 col 5
  bob()
  ^
  > 
  

So overall, I think it's actually pretty useful as-is?